In recent years, expectations for photoelectric conversion elements that directly convert sunlight energy into electric energy have been rapidly increased as a next generation of energy sources particularly from the viewpoint of environmental issues. Currently mainstream photoelectric conversion elements use silicon crystals.
Among them, an MWT (Metallization Wrap Through) photoelectric conversion element has been proposed in order to decrease the area occupation rate of a surface electrode and inhibit carrier recombination in an area below the surface electrode (Non-Patent Document 1). This MWT photoelectric conversion element has a structure in which a part of the surface electrode is arranged on the back side via a through-hole formed in a silicon substrate to allow decrease of the area occupation rate of the surface electrode.
A p-side electrode at a back side of one MWT photoelectric conversion element is connected with an n-side electrode at a back side of an adjacent MWT photoelectric conversion element by use of an interconnection foil to form a photoelectric conversion element assembly (Non-Patent Document 2). The interconnection foil has a patterned aluminum layer, and a surface of one part where the aluminum layer is electrically connected to each electrode at the back side of the MWT photoelectric conversion element is worked up so that an anti-corrosion layer is formed thereon, and the other part is coated with an isolating varnish. Conduction between each electrode at the back side of the MWT photoelectric conversion element and the anti-corrosion layer is made via a conductive adhesive.    Non-Patent Document 1: “A SYSTEMATIC APPROACH TO REDUCE PROCESS-INDUCED SHUNTS IN BACK-CONTACTED MC-SI SOLAR CELLS”, IEEE 4th World Conference on Photovoltaic Energy Conversion, U.S.A., 2006, pages 1319-1322, Filip Granek et al.    Non-Patent Document 2: “SINGLE-STEP LAMINATED FULL-SIZE PV MODULES MADE WITH BACK-CONTACTED MC-SI CELLS AND CONDUCTIVE ADHESIVES”, 19th European Photovoltaic Solar Energy Conference, France, 2004, pages 2145-2148, P. C. de Jong et al.